Contkol system



` July 15, 1941. J, K, CLARK 2,249,682

CONTROL SYSTEM Filed April 2, 1940 2 sheets-sheet 1 gag. n gaga @umm 2Sheets-Sheet 2 J. K. CLARK CONTROL SYSTEM Filed April 29, 1940 im xmJuly l5, 1941.

James KCcwk www.

Patented July 15, 1941 CONTROL SYSTEM James K. Clark, Utica, N. Y.,assignor to The Partlow Corporation, New Hartford, N. Y.

Application April 29, 1940, Serial No. 332,339

7 Claims.

This invention relates to control systems and more `particularly to ametering or like means for controlling and maintaining the conditions ofthe system constant within very close limits.

In accordance with this invention a metering control mechanism isprovided wherein an indicator cooperates with a graduated scale to showthe conditions of the system, the control meter being provided with asettable member cooperating with the scale at the point corresponding tothe particular conditions in the system which it is desired to maintainconstant. In cooperation with the indicator and settable member are yacontrol circuit and circuit interrupter, the latter functioning when theindicator approaches the indication of the predetermined conditiondesired to be maintained, and in order that the conditions may bemaintained within such very close limits, the circuit interrupter iscyclicly actuated to periodically interrupt the control circuit forperiods of increasing magnitude as the indicator approaches theindication of the condition determined by the position of the setta'blemember. The maximum of the magnitude of interruption of the circuit isadjustable whereby the control may be adjusted in accordance with theload on the system when desirable.

While the invention is subject to general application for controllingloads such as electrical loads, pressures, fluid flow and the like Ihave disclosed same 4applied in a control system for regulatingtemperatures, wherein the control is applied to the regulation of theflow of heating fluid, and preferably for regulating electric currentemployed as the heating medium.

The operation is such that the heat supplied to the device beingcontrolled, is modulated or controlled in such la manner that a changein temperature within a preselected band or zone of control will producea corresponding change in the rate that heat is supplied. That is tosay, the rate of heat being supplied the device is a function of thetemperature within a preselected band or zone of control. This issomewhat lanalogous to the control of water level in a tank by means ofa oat and valve. If water is allowed to drain from the tank, the floatwill drop a small amount and allow water to enter at the top at the samerate that is being drawn from the bottom. If a slightly greater amountis drawn the float will drop slightly and increase the rate of the waterflowing in until the two are again in balance. The band or zone ofcontrol above mentioned would be the difference in the tank levelbetween the all on and the all oil positions of the valve, since nocontrol would be exercised beyond these points in either direction.

The operation of the `present temperature control system, in the case ofelectric heat, is by automatic means to periodically start and stop theflow of current in such sequence that the proportion of time between thetime the current is on to the time it is off is such as to just satisfythe requirement for heat. If the temperature should drop slightly, thecontrol will cause the current to remain on slightly longer in eachimpulse and the off period will be lshortened an equal amount. Thefrequency of the on and off cycle is so chosen that there will be noperceptible drop in temperature between successive on impulses. Therewill be sufficient thermal inertia in the heater and its load to smoothout any tendency for a temperature ripple due to the periodic startingand stopping of the heat supply.

Further objects, details, and advantages of the invention will be morefully set forth in the following specification of a control system forregulating temperatures in conjunction with the accompanying drawingsand claims hereinafter.

In the drawings:

Fig. 1 is a front elevation view of an indicating and controlling meterfor temperature regulation in a control system in accordance with myinvention with the front cover thereof removed,

Fig. 2 is an intermediate vertical sectional view thereof, certain ofthe elements toward the rear being shown in front elevation,

Fig. 3 is a vertical side sectional view thereof, showing elements inside elevation,

Fig. 4 is an enlarged detail front elevational View illustrating themeter control elements of the system in cooperative relationship,`

Fig. 5 is a diagrammatic view illustrating the control circuits for thecontrol system,

Fig. 6 is a diagrammatic View illustrating the control system applied tothe control of fluid fuel as the heating medium in a temperatureregulator s stem in accordance with my invention.

Referring to the drawings, as best shown in Fig. 1, the system includesa control meter I0, connected with an expansible type of thermal elementII, which is adapted to be `positioned in a receptacle or the like,heated by a fluid fuel or an electric heating element and wherein thetemperature is to be maintained at a predetermined constant temperature.rThis thermal element II communicates by way of a conducting element I2to a diaphragm or plunger I3 in a cylinder or receptacle I4 on thebottom of the meter casing I5 and the elevation of the upper end ofplunger i3 is variable by the pressure medium or the like as afforded bythe thermally expansive iiuid in element Si, which moves in accordancewith the temperature being measured. This movementJ of plunger I3 istransferred to an indicator I 6, which cooperates with a scale I1graduated to indicate temperatures within the receptacle, that is,functions oi the pressure or expansion of the expansive fluid or othermedium in the thermostatically operating elements.

The control meter I9, as shown in Figs. 1 and 3 has its casing I5 ofsuitable formation for housing the indicating and control elements andis provided with a iront cover I3 (Fig. 3) secured to the housing partin which the elements are mounted in a manner so that it may be removedin order to adjust elements when required. Cover I3, has a sight openingI 9, for viewing the indications on the temperature scale I'I and atransparent cover 2G provides a closure for this opening.

Pls shown, indicator I-S is mounted to swing about an axis ZI, which isconcentric with the temperature scale I'I, and is yieldingly urgedtoward the left hand or lower end of the scale by means oi a spring 22,coiled around its axis shaft with its ends cooperating with a screw orprojection 23 on the lower portion of the indicator', and with theelement supporting base member 24, which is suitably secured in thebottom of casing I5. The operating connection between plunger I3 andindicator I6 for swinging it for indications on scale I1 comprises alink element 25 hating a longitudinally adjustable screw element 2S atits lower end for engagement with plunger I3 and having its upper endpivotally connected with a lever 2'1. Lever 2`I is pivoted at one end toan upright 28 of base 24 and its outer end is pivoted to a link 29 whichin turn is pivotally connected to an arm 33 extending laterally from thelower end of indicator I6. By means oi this linkage operating means,vertical lineal movements of plunger I3 are multiplied and translatedinto oscillatory movement iinparted to indicator IG, in a substantiallyconstant ratio, and the position of the indicator thereby cooperateswith scale I'I to indicate a function of the movement or positions ofplunger i3 which are functions of temperatures being measured. It willbe observed that adjustment of the indicator with respect to thethermally expansive elements may be obtained by changing the length oflink 25 through adjustment of the longitudinally adjustable screwelement 23, whereby the instrument may be properly calibrated.

Also cooperating with temperature scale I'I is a settable member 3l,having an indicator 32 comprising a point or as shown a pair of spacedpoints dening an operating zone or band, which points or points arepositionable along the graduations of scale Il. A rearwardly anddownwardly extending arm 33 of settable member 3| is journaled on ashaft centered with respect to axis 2l referred to heretofore. Thismounting of arm 33 includes a hub member 34 having a gear sector and abrake drum sector 35. An operating shaft journaled in bearing uprights3S extending from base 24. is provided at its inner end with a piniongear 3S meshing with gear sector 35, and its outer end extends throughan opening in the housing cover I8, where it is provided with a handle4I) for manually turning the shaft to swing the settable member to anydesired position with respect to graduated scale I'I.

Cooperating with brake drum sector 36 is a brake shoe 4I which ispressed into engagement with sector 36 by means of springs surroundingstuds 42 extending from base 24, which irictional means preventsmovement of the settable member except by manual operation of operatingshait 37.

Cooperating with indicator I5 and settable member 3i is a switch 43 anda switch opening member 44. Switch 43 is peierably carried by indicatorI5, and conveniently consists of switch contact carrying blades 45 and45, the latter having an extension 4l which is adapted to be engaged byopening member 44, ior separating the switch contacts for opening acontrol circuit of the control system as will hereinafter described.

Switch opening member 44 is carried by an arm 4S in the form of amounting plate, the lower end of which is secured to a hub 43 journaledon the shaft having center axis 2 I, so that its swinging movements areconcentric with respect to movements of indicator I6 and the arm of thesettable member SI. A spring 50 coiled about hub 49 tends to swing arms48 to the left in the same manner spring 22 operates on indicator I5 butthis arm 48 is provided with a rearward projection 43a, which normallyengages arm 33 of settable member 3I for properly positioning the arm48, with switch opening member 44, with respect to the settable memberfor the required cooperation with switch 43 as indicator I6 approachesthe graduation point or zone o scale II on which settable member 3I ispositioned.

Switch opening member 44 comprises a substantially circulareccentrically mounted on a rotary shaft 5I of an actuator 52, whichcomprises a small motor (conveniently of the selfstarting alternatingclock type wherein the drive shaft has a speed of 1 R. P. M.) mounted onthe back of the mounting plate or arm 43 and is 0perable to drive thecam or opening member 44 at a uniform speed. This actuator motor 52 isadapted for continuous operation when the system is in operation, or atleast, whenever indicator i5 is in the vicinity of scttable member 3I`,

In operation, it will be seen that as indicator I5 approaches settablemember 3|, extension 41, of switch 43, approaches the switch openingmember and when it is close enough it is engaged thereby to open theswitch contacts, iirst for a short period followed by periods ofincreasing duration during each cycle of tl e cam as the indicatorcontinues to move toward the settable member. In a thermostaticallycontrolled system, where a control by the operation of switch 43 efiectsa cutting off of the heat, the indicator will come to rest at a point inthe op erating zone determined by the settable member where the onperiod is just suiiicient to supply heat energy to take care of heatlosses in the system.

This movement of the temperature indicating hand toward the cam justdescribed is in the sense of increasing temperature so that a reductionin the on interval of the cycle will tend to cause the temperature todrop by means later described. Conversely a movement of the temperatureindicator IB in the opposite sense, that is to say, a drop intemperature or a movement of the switch contacts in a direction. awayfrom the rotating cam 44, will in a like manner but reversed sense causethe contacts to remain on or contacted for a greater interval of thecycle and by said later described means to tend to produce an increasein the temperature. It will thus be readily seen that the period of timein which the contacts are closed in proportion to the cycle of onerotation of the cam is a function of the temperature and the instrumentwill tend to assume a point oi balance. .Any tendn ency for thetemperature to drop will cause a slight increase in the heat supplied tocause the temperature to be restored toward the balance point and viceversa.

While the switch opening period may be increased so as to be a greaterportion of each cycle of the actuator or cam or even the entire period,it is desirable that some energy be furnished to the systemperiodically, that is during each cycle of operation of the actuator. Toaccomplish this, indicator l is provided with a projection 53 which isengageable with a stop 5f! carried by arm 48 whereby movement ofindicator IB with respect to the switch opening member 44 is limited andthereby the duration of the opening of the switch contacts for eachactuation cycle of the opening member. Stop 54 includes an adjustableengagement screw 5de whereby the opening period may be adjusted asdesired, or as short as desired, depending on the load in the system,surges, and other factors. In case the indicator I5 should continue tomove after engagement with stop 5d, as may occur under certaincircumstances arm 48 carrying switch opening member 44 is also movedthereby, as permitted by its yieldable engagement with the settablemember arm However, under normal operation the adjustment is such thatthis eXtra movement will not occur, and the desired control ismaintained within very close limits.

While control of a heat supply by control meter I5 in a heat controlsystem as referred to is applicable to a control valve for fluid fuels,it is preferably applied for controlling electric current employed as aheating medium, and Fig. 5 shows a suitable circuit arrangement fordoing so. A source of electric power is supplied to the lines 55 and 56at 51.

Lines 55 and 59 are connected with the heating element or load 5B.Intermediate, the control meter lil and a heavy current relay 5S,diagram-- matically represented, are connected with the lines forcontrolling the load current. A relay of the type shown in the patent toMcKinney No. 2,142,522 has been found satisfactory in a control systemrequiring a moderate heating load current, and as diagrammatically shownincludes switch circuit conductors 52 and S3, which when the circuit isclosed therebetween, completes the circuit between lines 55 and to whichthey are respectively connected and thereby current is applied to theload.

This relay GQ, in general as diagrammatically illustrated, includes acylindrical magnetic plunger 5l for displacing mercury, so as to closethe circuit between terminals or electrodes 62 and B3 for completing thecircuit between the line conductors 55 and 59. The relay also has anoperating coil 64 for electromagnetically ef1 fecting the plunging ofplunger E! into the Inercury to effect an elevation of the mercury forcompleting the circuit for carrying the load current required by anelectric heating element of the thermally controlled system.

Control meter l0 operates to control the operation of relay 60. Theelectric circuits in this meter include conductors 65 and E5 connectedwith power lines 55 and 56 and with the switch actuator motor 52,whereby in the event it is a clock type of A. C. motor it iscontinuously operated at a synchronous speed as referred to heretofore.A relay operating control circuit also extends through this controlmeter and comprises a conductor 61 connected with power line 55 andblade 45 of switch 43 on indicator I6; thence the circuit continuesthrough normally closed contacts of switch blades 45 and 46, switchblade 45 to conductor 68, through a condenser B9, conductor 10energizing coil 54 of relay 50, to a branch conductor 'Il of power line'56, whereby suiiicient current is passed through the operating coil toeffect the actuation of plunger 6i for closing the relay circuit.

It is to be noted that the circuit just described for operating relay 6Uis such as to draw a very small current through the contacts of switch43 in control meter lil, the condenser ES, materially lowering thecurrent which would otherwise pass as is required to effect theoperation of plunger 6I of relay Si). This is supplemented however by acircuit shunting the control circuit through the meter switch contacts,comprising a resistance 'i2 connected by conductor 'I3 with power line55 and conductor 'i4 with conductor 10, whereby a small current which byitself is insufficient to operate relay plunger 5 I, is continuouslyflowing through operating coil E4, and when this is supplemented bycurrent afforded by closing of contacts or switch 43 in control meterl5, the current in coil 54 is sufiicient to effect the actuation ofplunger 5l. Conversely when the contacts of switch 4.5 are opened thecurrent in relay operating ccil 64 is reduced sufficiently to eiect animmediate release of plunger 6l to break the circuit between electrodes52 and B3 to completely cut off the current to the load or electricheating element.

In the automatic control of temperature where electric heat is used,heretofore it has been customary to cause the temperature control instrument to make and .break the heating circuit as required, that is to say,when the temperature reached the control point, the heating current wascompletely cut oil? and when the temperature dropped suflciently tooperate the instru.- ment contacts, the maximum heating current wasagain allowed to flow. rl'hus, altho a slight amount of additional heatbe required to restore the temperature, the control operated to allowthe maximum capacity of the heater to flow, thereby supplying more heatthan was required and causing the temperature to rise to a point wherethe control again would cut it off. The thermal inertia of the heaterand its load would therefore cause the temperature to continue to riseor overshoot at each cut-off of the cycle. Then. since the heat supplyhas been cut completely ou the temperature would drop until the controlinstrument again closed its contacts to again supply heat. Again, thethermal inertia would act to allow the temperaure to continue to fallfor a period after the heat supply had again been restored. Thus since adefinite amount of rise and fall of temperature was required to operatethe instrument contacts and because of the effects of thermal inertiajust described, there was a constant rising and falling of temperatureabove and below an average control temperature.

By the present invention above described, this fluctuation is reduced toa minimum and in the case where the heat loss from the apparatus beingcontrolled is constant there is practically no fluctuation oftemperature, it being perceptible only by the most sensitive ofinstruments. This is due as explained above, to the fact that the rateheat is supplied to the apparatus is made a function of the degree ofdeviation of the temperature from the control point. Theref re theinstrument will automatically end to seek a point where the rate of heatlost or extracted from the apparatus under control, and to maintain thispoint until a change occurs in either' of said rates.

Control meter ib is also applicable to gaseous or liquid iuels, in whichcase an electrically opcrated valve 'E5 in the fuel line as shown in Gis substituted for the electric heating unit in the system abovedescribed. W'hen so arranged the or liquid would be periodically allowedto new and to cease much in the same nanner as the electric current wasallowed to flow and cease above. es indicated duid fuel may be suppliedby pipe to valve 'l5 and from there by pipe Tl' to the burner. Thisvalve is oi the normally closed type but is shown in open position beineretained thereby by solenoid operating means 'i8 the coil of which isconnected in the control circuit of a control meter IG. In this controlmeter the switch contacts of the control circuit are arranged to remainclosed until the indicator i5 moves adjacent to the settable memberwhereupon the fuel control valve H5 is cyclicly operated as hereinbefore set forth.

I do not wish to limit myself to any of the speci' c constructions ormodes oi operation described which are for purpose of giving examples orillustrations of employment of the invention, since it will be obviousthat wide departure from the above may be made without departing fromthe spirit and scope of the invention set iorth in the following claims.

What is claimed is:

l. In an electric control system, a graduated scale on which conditionsor the system may be indicated, a settable member cooperating with thescale and movable with respect thereto to any predetermined stationaryposition along the scale, an indicator cooperating with the scale toindicate the condition in the system, means for moving the indicatoralong the scale in accordance with the conditions of the system, acircuit lor controlling the conditions in the system including a switchcarried by the indicator ncrmally closed while the indicator iscooperating with the low side oi the scale with respect to thepredetermined condition of the system determined by the position of thesettable member, a switch opening member associated with the settablemember, and means for actuating said switch opening member so as toperiodically open said switch when the indicator is adjacent to thesettable member.

2. In an electric control system, a graduated scale on which conditionsof the system may be indicated, a settable member cooperating with thescale and movable with respect thereto to any predetermined stationaryposition along the scale, an indicator cooperating with the scale toindicate the condition in the system, means for moving the indicatoralong the scale in accordance with the conditions of the system, acircuit for controlling the conditions in the system including a switchcarried by the indicator normally closed while the indicator iscooperating with the low side of the scale vith respect to thepredetermined condition ol the system determined by the position of thesettable member, a switch opening member associated with the settablemember, means for actuating said switch opening member so as toperiodically open said switch when the indicator is adjacent to thesettable member, and adjusting means cooperating between the switchopening member and indicator whereby the duration of the open periods ofthe switch during each cycle of operation of the switch actua-ting meansmay be determined.

3. In an electric control system, a graduated scale on which conditionsof the system may be indicated, a settable member cooperating with thescale and movable with respect thereto to any predetermined stationaryposition along the scale, an indicator cooperating with the scale toindicate the condition in the system, means for moving the indicatoralong the scale in accordwlth the condition of the system, a circuit forcontrolling the condition of the system including means operable by theindicator for varying said circuit in a manner to produce changes ofgreater or less relative magnitude to the system with respect to thepredetermined condition of the system determined by the position of thesettable member, a member engaging the settable member and movabletherewith, a spring maintaining said member in engagement with thesettable member in a manner to permit it to be moved away therefromalong the high side of the scale beyond the settable member in the eventthe indicator moves to the high side of the scale beyond the settablemember, and means carried by said member for periodically varying saidcircuit so that the duration of the changes are functions of theindicator positions with respect to the settable member when adjacent toeach other.

4. In an electric control system, a graduated scale on which conditionsof the system may be indicated, a settable member cooperating with thescale and movable with respect thereto to any predetermined stationaryposition along the scale, an indicator cooperating with the scale toindicate the condition in the system, means for moving the indicatoralong the scale in accordance with this condition of the system, acircuit for controlling the conditions in the system including a switchcarried by the indicator nor mally closed while the indicator iscooperating with the low side of the scale with respect to thepredetermined condition of the system determined by the position of thesettable member, a switch opening member yieldably engaging theset-table member operable to open said switch when the indicator isadjacent to the settable member and adapted to be moved along the highside of the scale beyond the settable member in the event the indicatormoves to the high side of the scale beyond the settable member, andmeans for actuating said switch opening member so as to periodicallyopen said switch when the indicator is in a position for the switchopening member to cooperate with the switch.

5. In an electric control system, a graduated scale on which conditionsoi the system may be indicated, a settable member cooperating with thescale and movable with respect thereto to any predetermined stationaryposition along the scale, an indicator cooperating with the scale toindicate the condition in the system, means for moving the indicatoralong the scale in accordance with this condition of the system, acircuit for controlling' the conditions in the system including a switchcarried by the indicator normally closed while the indicator iscooperating with the low side of the scale with respect to thepredetermined condition of the system determined by the position of thesettable member, a switch opening member yieldably engaging the settablemember operable to open said switch when the indicator is adjacent tothe settable member and adapted to be moved along the high side of thescale beyond the settable member in the event the indicator moves to thehigh side of the scale beyond the settable member, means for actuatingsaid switch opening member so as to periodically open said switch whenthe indicator is in a position for the switch opening member tocooperate with the switch, and adjusting means cooperating between theswitch opening member and indicator whereby the duration of the openperiods of the switch during each cycle of operation of the switchactuating means may be determined.

6. A control meter for an electric control system in accordance Withclaim 1, including a meter housing wherein the indicator, scale,settable member and switch opening member are mounted and housed, saidswitch opening member including an arm normally swingable with thesettable member, a cam switch opening element carried by the arm, amotor carried by the arm for rotating said cam at a substantiallyconstant speed, and actuating means connected With the meter for movingthe indicator.

7. In an electric control system, a graduated scale on which conditionsof the system may be indicated, a settable member cooperating with thescale and movable with respect thereto to any predetermined stationaryposition along the scale, an indicator cooperating with the scale toindicate the condition in the system, means for moving the indicator.along the scale in accordance with the condition of the system, acircuit for controlling the condition of the system including meansoperable by the indicator for Varying said circuit in a manner toproduce changes of greater or lesser relative magnitude to the systemwith respect to the predetermined condition of the system determined bythe position of the settable member, yieldable means engaging thesettable member and movable therewith and adapted to be moved awaytherefrom along the high side of the scale beyond the settable member inthe event the indicator moves to the high side of the -scale beyond thesettable member, and means carried by said yieldable means forpericdically varying said circuit so that the duration of the changesare functions of the indicator positions with respect to the settablemember when adjacent to each other.

JAMES K. CLARK.

